US20190353217A1 - Friction material - Google Patents
Friction material Download PDFInfo
- Publication number
- US20190353217A1 US20190353217A1 US16/299,363 US201916299363A US2019353217A1 US 20190353217 A1 US20190353217 A1 US 20190353217A1 US 201916299363 A US201916299363 A US 201916299363A US 2019353217 A1 US2019353217 A1 US 2019353217A1
- Authority
- US
- United States
- Prior art keywords
- clusters
- fibres
- mmvf
- friction material
- fibre
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000002783 friction material Substances 0.000 title claims abstract description 118
- 239000000835 fiber Substances 0.000 claims abstract description 105
- 238000000034 method Methods 0.000 claims abstract description 24
- 239000000203 mixture Substances 0.000 claims description 81
- 238000009472 formulation Methods 0.000 claims description 40
- 238000009826 distribution Methods 0.000 claims description 14
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 9
- 238000002360 preparation method Methods 0.000 claims description 8
- 239000000377 silicon dioxide Substances 0.000 claims description 4
- 239000007858 starting material Substances 0.000 claims description 4
- 229910052681 coesite Inorganic materials 0.000 claims description 3
- 229910052593 corundum Inorganic materials 0.000 claims description 3
- 229910052906 cristobalite Inorganic materials 0.000 claims description 3
- 229910052682 stishovite Inorganic materials 0.000 claims description 3
- 229910052905 tridymite Inorganic materials 0.000 claims description 3
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 3
- 239000007788 liquid Substances 0.000 description 39
- 239000011230 binding agent Substances 0.000 description 34
- 229920005989 resin Polymers 0.000 description 26
- 239000011347 resin Substances 0.000 description 26
- 238000012360 testing method Methods 0.000 description 25
- 229910000831 Steel Inorganic materials 0.000 description 22
- 238000002156 mixing Methods 0.000 description 22
- 239000010959 steel Substances 0.000 description 22
- 230000003014 reinforcing effect Effects 0.000 description 13
- 238000001035 drying Methods 0.000 description 10
- 239000000047 product Substances 0.000 description 10
- 239000003082 abrasive agent Substances 0.000 description 9
- 239000000945 filler Substances 0.000 description 9
- 229920003235 aromatic polyamide Polymers 0.000 description 8
- 229910052500 inorganic mineral Inorganic materials 0.000 description 7
- 239000011707 mineral Substances 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- 229920001568 phenolic resin Polymers 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 238000005588 Kraus reaction Methods 0.000 description 6
- 229920000914 Metallic fiber Polymers 0.000 description 6
- 239000000314 lubricant Substances 0.000 description 6
- 238000007873 sieving Methods 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 5
- 239000000654 additive Substances 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 5
- 229920001577 copolymer Polymers 0.000 description 5
- NJLLQSBAHIKGKF-UHFFFAOYSA-N dipotassium dioxido(oxo)titanium Chemical compound [K+].[K+].[O-][Ti]([O-])=O NJLLQSBAHIKGKF-UHFFFAOYSA-N 0.000 description 5
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 4
- 229920000180 alkyd Polymers 0.000 description 4
- 239000000428 dust Substances 0.000 description 4
- 239000000839 emulsion Substances 0.000 description 4
- 229920003986 novolac Polymers 0.000 description 4
- 239000005011 phenolic resin Substances 0.000 description 4
- 238000003825 pressing Methods 0.000 description 4
- OCKGFTQIICXDQW-ZEQRLZLVSA-N 5-[(1r)-1-hydroxy-2-[4-[(2r)-2-hydroxy-2-(4-methyl-1-oxo-3h-2-benzofuran-5-yl)ethyl]piperazin-1-yl]ethyl]-4-methyl-3h-2-benzofuran-1-one Chemical compound C1=C2C(=O)OCC2=C(C)C([C@@H](O)CN2CCN(CC2)C[C@H](O)C2=CC=C3C(=O)OCC3=C2C)=C1 OCKGFTQIICXDQW-ZEQRLZLVSA-N 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 229910001369 Brass Inorganic materials 0.000 description 3
- -1 alkyl silicate Chemical compound 0.000 description 3
- 239000004760 aramid Substances 0.000 description 3
- 239000010951 brass Substances 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 229920002678 cellulose Polymers 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 229920001971 elastomer Polymers 0.000 description 3
- 239000003822 epoxy resin Substances 0.000 description 3
- 239000003365 glass fiber Substances 0.000 description 3
- 239000004816 latex Substances 0.000 description 3
- 229920000126 latex Polymers 0.000 description 3
- 239000000395 magnesium oxide Substances 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- 239000010445 mica Substances 0.000 description 3
- 229910052618 mica group Inorganic materials 0.000 description 3
- 229920000647 polyepoxide Polymers 0.000 description 3
- 239000004814 polyurethane Substances 0.000 description 3
- 229920000915 polyvinyl chloride Polymers 0.000 description 3
- 230000002787 reinforcement Effects 0.000 description 3
- 239000005060 rubber Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000004575 stone Substances 0.000 description 3
- 229920003048 styrene butadiene rubber Polymers 0.000 description 3
- 239000004094 surface-active agent Substances 0.000 description 3
- 239000000080 wetting agent Substances 0.000 description 3
- 244000226021 Anacardium occidentale Species 0.000 description 2
- FERIUCNNQQJTOY-UHFFFAOYSA-N Butyric acid Chemical compound CCCC(O)=O FERIUCNNQQJTOY-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 229920000271 Kevlar® Polymers 0.000 description 2
- 239000004113 Sepiolite Substances 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910000019 calcium carbonate Inorganic materials 0.000 description 2
- 235000020226 cashew nut Nutrition 0.000 description 2
- 239000001913 cellulose Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 description 2
- 238000010348 incorporation Methods 0.000 description 2
- 239000004761 kevlar Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 2
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 2
- 229920002037 poly(vinyl butyral) polymer Polymers 0.000 description 2
- 229920005990 polystyrene resin Polymers 0.000 description 2
- 229920002635 polyurethane Polymers 0.000 description 2
- 229920002689 polyvinyl acetate Polymers 0.000 description 2
- 239000011118 polyvinyl acetate Substances 0.000 description 2
- 229940075065 polyvinyl acetate Drugs 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 229910052624 sepiolite Inorganic materials 0.000 description 2
- 235000019355 sepiolite Nutrition 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910010271 silicon carbide Inorganic materials 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 229920001187 thermosetting polymer Polymers 0.000 description 2
- 239000010455 vermiculite Substances 0.000 description 2
- 229910052902 vermiculite Inorganic materials 0.000 description 2
- 235000019354 vermiculite Nutrition 0.000 description 2
- 210000002268 wool Anatomy 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- OEPOKWHJYJXUGD-UHFFFAOYSA-N 2-(3-phenylmethoxyphenyl)-1,3-thiazole-4-carbaldehyde Chemical compound O=CC1=CSC(C=2C=C(OCC=3C=CC=CC=3)C=CC=2)=N1 OEPOKWHJYJXUGD-UHFFFAOYSA-N 0.000 description 1
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- GZVHEAJQGPRDLQ-UHFFFAOYSA-N 6-phenyl-1,3,5-triazine-2,4-diamine Chemical compound NC1=NC(N)=NC(C=2C=CC=CC=2)=N1 GZVHEAJQGPRDLQ-UHFFFAOYSA-N 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 239000004971 Cross linker Substances 0.000 description 1
- 239000001856 Ethyl cellulose Substances 0.000 description 1
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 1
- 108010010803 Gelatin Proteins 0.000 description 1
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- 244000068988 Glycine max Species 0.000 description 1
- 235000010469 Glycine max Nutrition 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 1
- 239000000020 Nitrocellulose Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 229920001328 Polyvinylidene chloride Polymers 0.000 description 1
- 239000002174 Styrene-butadiene Substances 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 229920001807 Urea-formaldehyde Polymers 0.000 description 1
- 229920002433 Vinyl chloride-vinyl acetate copolymer Polymers 0.000 description 1
- 229920001986 Vinylidene chloride-vinyl chloride copolymer Polymers 0.000 description 1
- 150000001252 acrylic acid derivatives Chemical class 0.000 description 1
- 238000004026 adhesive bonding Methods 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 239000010425 asbestos Substances 0.000 description 1
- 239000007767 bonding agent Substances 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 239000005018 casein Substances 0.000 description 1
- BECPQYXYKAMYBN-UHFFFAOYSA-N casein, tech. Chemical compound NCCCCC(C(O)=O)N=C(O)C(CC(O)=O)N=C(O)C(CCC(O)=N)N=C(O)C(CC(C)C)N=C(O)C(CCC(O)=O)N=C(O)C(CC(O)=O)N=C(O)C(CCC(O)=O)N=C(O)C(C(C)O)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=N)N=C(O)C(CCC(O)=O)N=C(O)C(CCC(O)=O)N=C(O)C(COP(O)(O)=O)N=C(O)C(CCC(O)=N)N=C(O)C(N)CC1=CC=CC=C1 BECPQYXYKAMYBN-UHFFFAOYSA-N 0.000 description 1
- 235000021240 caseins Nutrition 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- UHZZMRAGKVHANO-UHFFFAOYSA-M chlormequat chloride Chemical compound [Cl-].C[N+](C)(C)CCCl UHZZMRAGKVHANO-UHFFFAOYSA-M 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- BWFPGXWASODCHM-UHFFFAOYSA-N copper monosulfide Chemical compound [Cu]=S BWFPGXWASODCHM-UHFFFAOYSA-N 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 239000004643 cyanate ester Substances 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
- 239000004815 dispersion polymer Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- UHESRSKEBRADOO-UHFFFAOYSA-N ethyl carbamate;prop-2-enoic acid Chemical compound OC(=O)C=C.CCOC(N)=O UHESRSKEBRADOO-UHFFFAOYSA-N 0.000 description 1
- 229920001249 ethyl cellulose Polymers 0.000 description 1
- 235000019325 ethyl cellulose Nutrition 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 235000013312 flour Nutrition 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 125000001153 fluoro group Chemical group F* 0.000 description 1
- SLGWESQGEUXWJQ-UHFFFAOYSA-N formaldehyde;phenol Chemical compound O=C.OC1=CC=CC=C1 SLGWESQGEUXWJQ-UHFFFAOYSA-N 0.000 description 1
- 229920000159 gelatin Polymers 0.000 description 1
- 239000008273 gelatin Substances 0.000 description 1
- 235000019322 gelatine Nutrition 0.000 description 1
- 235000011852 gelatine desserts Nutrition 0.000 description 1
- 239000000156 glass melt Substances 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- WTFXARWRTYJXII-UHFFFAOYSA-N iron(2+);iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[Fe+2].[Fe+3].[Fe+3] WTFXARWRTYJXII-UHFFFAOYSA-N 0.000 description 1
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- XCAUINMIESBTBL-UHFFFAOYSA-N lead(ii) sulfide Chemical compound [Pb]=S XCAUINMIESBTBL-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002734 metacrylic acid derivatives Chemical class 0.000 description 1
- 229910052976 metal sulfide Inorganic materials 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052863 mullite Inorganic materials 0.000 description 1
- 229920001220 nitrocellulos Polymers 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 229920003227 poly(N-vinyl carbazole) Polymers 0.000 description 1
- 229920000090 poly(aryl ether) Polymers 0.000 description 1
- 229920002492 poly(sulfone) Polymers 0.000 description 1
- 229920006350 polyacrylonitrile resin Polymers 0.000 description 1
- 229920006122 polyamide resin Polymers 0.000 description 1
- 229920001230 polyarylate Polymers 0.000 description 1
- 229920005668 polycarbonate resin Polymers 0.000 description 1
- 239000004431 polycarbonate resin Substances 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 239000009719 polyimide resin Substances 0.000 description 1
- 229920001228 polyisocyanate Polymers 0.000 description 1
- 239000005056 polyisocyanate Substances 0.000 description 1
- 229920001195 polyisoprene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920005862 polyol Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 150000003077 polyols Chemical class 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 229920001290 polyvinyl ester Polymers 0.000 description 1
- 229920001289 polyvinyl ether Polymers 0.000 description 1
- 239000005033 polyvinylidene chloride Substances 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 1
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- KCTAWXVAICEBSD-UHFFFAOYSA-N prop-2-enoyloxy prop-2-eneperoxoate Chemical compound C=CC(=O)OOOC(=O)C=C KCTAWXVAICEBSD-UHFFFAOYSA-N 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 229910052895 riebeckite Inorganic materials 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 229920002545 silicone oil Polymers 0.000 description 1
- 229920002050 silicone resin Polymers 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
- 229910052851 sillimanite Inorganic materials 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- YPMOSINXXHVZIL-UHFFFAOYSA-N sulfanylideneantimony Chemical compound [Sb]=S YPMOSINXXHVZIL-UHFFFAOYSA-N 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- AFNRRBXCCXDRPS-UHFFFAOYSA-N tin(ii) sulfide Chemical compound [Sn]=S AFNRRBXCCXDRPS-UHFFFAOYSA-N 0.000 description 1
- 229920006337 unsaturated polyester resin Polymers 0.000 description 1
- 239000002966 varnish Substances 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D69/00—Friction linings; Attachment thereof; Selection of coacting friction substances or surfaces
- F16D69/02—Compositions of linings; Methods of manufacturing
- F16D69/025—Compositions based on an organic binder
- F16D69/026—Compositions based on an organic binder containing fibres
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
- C03C25/10—Coating
- C03C25/24—Coatings containing organic materials
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
- C03C25/10—Coating
- C03C25/48—Coating with two or more coatings having different compositions
- C03C25/50—Coatings containing organic materials only
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/062—Glass compositions containing silica with less than 40% silica by weight
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
- C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
- C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D65/00—Parts or details
- F16D65/02—Braking members; Mounting thereof
- F16D65/04—Bands, shoes or pads; Pivots or supporting members therefor
- F16D65/092—Bands, shoes or pads; Pivots or supporting members therefor for axially-engaging brakes, e.g. disc brakes
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D2200/00—Materials; Production methods therefor
- F16D2200/0034—Materials; Production methods therefor non-metallic
- F16D2200/0039—Ceramics
- F16D2200/0043—Ceramic base, e.g. metal oxides or ceramic binder
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D2200/00—Materials; Production methods therefor
- F16D2200/0034—Materials; Production methods therefor non-metallic
- F16D2200/0056—Elastomers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D2200/00—Materials; Production methods therefor
- F16D2200/006—Materials; Production methods therefor containing fibres or particles
- F16D2200/0065—Inorganic, e.g. non-asbestos mineral fibres
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D2200/00—Materials; Production methods therefor
- F16D2200/006—Materials; Production methods therefor containing fibres or particles
- F16D2200/0069—Materials; Production methods therefor containing fibres or particles being characterised by their size
Definitions
- the invention relates to a friction material exhibiting reduced wear in use and to processes for preparation of such a friction material.
- the invention also relates to man-made vitreous fibre (MMVF) clusters suitable for use in preparation of these friction materials and for reduction of wear of the friction materials.
- MMVF man-made vitreous fibre
- Friction materials are widely used in a variety of applications such as in brake or clutch devices. They are often used for instance in the form of brake pads, brake shoes, brake linings, friction plates and clutch facings. They may be used in a variety of applications including industrial machines and transport machines or vehicles such as elevators, passenger vehicles and the like.
- One important characteristic of a friction material is that it should exhibit low wear in use. Wearing of the friction material can lead to an increase in emissions, which is undesirable.
- the present invention aims to produce friction materials which exhibit reduced wear.
- WO2011/042533 describes the use of inorganic fibre balls in a friction material for the purpose of reducing NVH (noise and vibration harshness). This document teaches to use normal lubricants and abrasives as fillers to adjust the wear properties of the friction material. There is also no requirement for the inorganic fibre balls to have any particular size distribution.
- MMVF man-made vitreous fibres
- the fibres are incorporated as “loose” fibres and are of lower abrasiveness than other MMVF commonly used in friction materials such as brake pads, thereby reducing the wear.
- MMVF MMVF-co-polymer
- the present invention is based on the finding that inclusion of MMVF in the form of discrete clusters in the friction material formulation can lead to reduced wear, in comparison with including MMVF in the form of loose fibres.
- MMVF clusters in a friction material formulation for the reduction of wear of said friction material in use.
- a friction material containing MMVF in the form of clusters will exhibit reduced wear in use in comparison with a friction material having the same formulation but containing the same percentage of the same MMVF in loose form. Wear can be determined according to standard tests such as the wear elements of SAE J2521: 2003-06, SAE J 2522: 2006-01, and SAE J 2707: 2005-02.
- Fibres of the MMVF type when incorporated into friction materials are conventionally included as loose fibres, namely single individual fibres which are not substantially entangled with each other.
- loose fibres When included in a matrix, such loose fibres are sometimes referred to as dispersed fibres, because they are dispersed throughout the matrix.
- the fibre clusters used according to the present invention are balls of agglomerated MMVF, which may be to some extent interwoven or entangled. They may therefore have the form of granules. Preferably they are regular in shape, for instance ovoid or spheroid (substantially spherical). When incorporated into a friction material, they may have a discoid shape.
- a method for the preparation of a friction material comprising the step of incorporating MMVF clusters into a friction material formulation, wherein the MMVF clusters have a size distribution such that at least 95 wt % have size in the range 0.6 to 1.6 mm.
- the mixture may comprise at least 50 wt %, preferably at least 75 wt % and even 100 wt % MMVF in the form of clusters.
- the remainder is formed of MMVF in the form of loose fibres.
- At least 95 wt % of the MMVF clusters have a size in the range from 0.6 mm to 1.6 mm, preferably from 0.6 mm to 1.0 mm.
- Preferably all of the MMVF clusters used in the method have a size in that range. Size can be controlled using conventional sieving techniques. The size refers to the largest dimension of the man-made vitreous fibre clusters, which need not have a regular spherical shape.
- MMVF clusters within this narrow size range brings benefits for wear reduction when the friction material is in use.
- the wear of the friction material itself is reduced. This is of current concern in the automotive industry, in which it is desirable to reduce the wear of brake pads to reduce particulate emissions to the environment.
- Using MMVF clusters within this narrow size range may contribute to wear rate reduction due to the size of the reservoir provided by the MMVF clusters, in which wear debris may accumulate rather than being lost to the environment.
- the level of MMVF clusters is less than 15 wt %, such as less than 12 wt %. It is possible to include loose fibres as well as MMVF clusters. In this case, it is preferred that the loose fibres are also MMVF, more preferably of the same type and composition as the MMVF that are used to form the clusters. In this case, it is also preferred that the total level of MMVF clusters and loose fibres is less than 15 wt %, preferably less than 12 wt %.
- the level of MMVF clusters in the friction material is at least 1 wt %, preferably at least 3 wt %, more preferably at least 5 wt %.
- MMVF loose fibres and MMVF clusters are beneficial for achieving the wear reduction properties associated with the clusters alongside the strengthening properties associated with the loose fibres.
- MMVF clusters and loose MMVF are used, preferably at least 50 wt %, more preferably at least 75 wt %, of the blend is made up of MMVF clusters, with the balance being loose MMVF.
- the friction material may comprise other types of loose fibres, such as aramid fibres, steel fibres, carbon fibres, and other types of mineral fibres.
- other fibre types may be used as reinforcing fibres.
- a mixture of different types of reinforcing fibres with complementing properties are used.
- Examples for reinforcing fibres other than MMVF are glass fibres, mineral fibres, metallic fibres, carbon fibres, aramid fibres, potassium titanate fibres, sepiolite fibres and ceramic fibres.
- Metallic components for reinforcement may also have a shape other than a fibre shape. As is usual in the art, in the present application all metallic components included in the friction material are considered as metallic reinforcing fibres whatever the shape thereof is (fibre, chips, wool, etc.).
- metallic fibres examples include steel, brass and copper. Since steel fibres often suffer from the drawback of rusting, zinc metal is often distributed over the friction material when steel fibres are used.
- Metallic fibres may be oxidized or phosphatized.
- An example of aramid fibres are Kevlar fibres.
- Ceramic fibres are typically made of metal oxides such as alumina or carbides such as silicon carbide.
- all of the loose fibres are loose MMVF.
- the MMVF used to form the clusters preferably have length in the range of 100 to 650 ⁇ m, preferably 100 to 350 ⁇ m.
- Fibre clusters made from medium length fibres can result in a particularly stable coefficient of friction.
- Using fibre clusters made from short or medium length fibres (100-350 ⁇ m) can result in wear reduction compared to using loose fibres.
- Fibre diameter is also typically in the range 3 to 10 microns.
- the fibre diameter and fibre length of the plurality of man-made vitreous fibres that make up each MMVF cluster are both number averages.
- the aspect ratio is calculated as the number average length divided by the number average diameter.
- the number average fibre length is preferably no greater than 200 ⁇ m.
- the number average fibre diameter is preferably no less than 4.5 ⁇ m.
- the aspect ratio is preferably no greater than 60, more preferably no greater than 40, more preferably no greater than 30.
- the MMVF clusters are blended with the remainder of the friction material formulation in such a way as to remain as discrete and coherent clusters of MMVF in the final friction material.
- the friction material formulation is generally formed into the desired final form by moulding and compression.
- the MMVF clusters, and optionally any loose MMVF are incorporated into the mixture of components at the final mixing step prior to pressing and curing, to preserve the shape of the MMVF clusters.
- the MMVF clusters may be coated with a suitable bonding agent prior to mixing, such that the clusters' shape is preserved even when combining into the mixture at the same time as the other components of the friction material.
- the clusters remain as discrete and coherent clusters but rather than being of ovoid or substantially spherical form are in discoid form. Namely their diameter is often at least 3 times, sometimes at least 4 times the height. Height is defined as the direction within the friction material along which compression has been exerted.
- MMVF used for the fibre clusters in this invention may have a composition including for instance 35-45 wt % SiO 2 , 16-23 wt % Al 2 O 3 , 0.3-0.7 wt % TiO 2 , ⁇ 1.5 wt % Fe 2 O 3 , 20 to 30 wt % CaO, in particular 25-27 wt % CaO, 1 to 5 wt % MgO, in particular 3-7 wt % MgO, ⁇ 2.0 wt % Na 2 O, ⁇ 0.6 wt % K 2 O, ⁇ 0.3 wt % P 2 O 5 , ⁇ 0.2 wt % MnO. Chemical properties can be ascertained using XRF.
- Suitable types of MMVF for the MMVF clusters include stone fibres, glass fibres, slag fibres and ceramic fibres. Preferably stone fibres are used.
- the composition of the fibres making up the man-made vitreous fibre clusters comprises less than 50 wt % SiO 2 and greater than 15 wt % Al 2 O 3 . This may help to make the MMVF bio-soluble.
- the fibre clusters for use in the method of the invention preferably have a moisture content of less than 0.05 wt %.
- MMVF MMVF clusters
- the presence of the liquid enhances the firmness of the clusters obtained.
- the liquid used should be vaporizable. A low viscosity liquid is preferable. Examples for suitable liquids are water and organic solvents, e g alcohols, water based emulsions and mixtures thereof.
- Preferred liquids are water and water based emulsions.
- the liquid and the MMVF may be simply fed into the mixer. It is also possible to spray the liquid on the MMVF which may cause a better preliminary distribution of the liquid on the fibres. It is further preferred that the liquid employed contains a binder since the binder further improves the firmness of the MMVF clusters obtained.
- the MMVF used for preparing the MMVF clusters are preferably relatively short fibres, such as a length of 100 to 500 ⁇ m, preferably 100 to 350 ⁇ m otherwise the liquid cannot be distributed well on the fibre surface.
- the MMVF are in the form of loose MMVF or predominately in the form of loose MMVF.
- the MMVF are mixed with the liquid, preferably containing a binder, so that the liquid is distributed on the surface of the fibres.
- the MMVF are moved, preferably by a circular motion, so that the MMVF agglomerate or ball up, respectively, to form the MMVF clusters.
- the mixing step preferably comprises mixing the MMVF with the liquid, preferably containing the binder, and rolling the MMVF on which the liquid is distributed to form the MMVF clusters.
- the liquid supports the formation of the clusters.
- the mixing step may optionally comprise two stages: a first more vigorous mixing to achieve mixing of the liquid with the MMVF, and a second, more gentle, mixing or rolling in order to ball up the MMVF on which the liquid is distributed.
- the mixer employed in the mixing step may be any common mixing device generally known in the art, for instance a horizontal mixer or a vertical mixer. It may be useful that the mixer includes choppers, e.g. a vertical or horizontal mixer having choppers. Appropriately, the mixing time may be in the range of 1 to 20 minutes and preferably in the range of 2 to 8 minutes. Appropriately the head axle speed is in the range of 50-300 rpm.
- the mixing process preferably consists of a first stage with choppers rotation, e g., at 2500-3500 rpm or approximately at 3000 rpm, to distribute the liquid and a second stage without chopped activity for maximum ball formation.
- the mixing parameters however may vary depending on the type of MMVF, the mixer, the ball size desired, etc.
- the product obtained containing MMVF clusters needs to be dried when discharged from the mixer because products with a too high liquid content cannot be tolerated in friction materials.
- the liquid is evaporated from the MMVF clusters for which commonly known methods can be used, e g drying in an oven (static drying), drying in a dispersion dryer or drying in a fluid bed dryer.
- the drying step may result in a complete removal of the liquid, though a small amount of liquid remaining in the MVMF clusters may be acceptable.
- water is used as the liquid, the formed MMVF clusters are not very strong after drying so that the clusters may be opened too easily when they are mixed into a friction material formulation if the mechanical load is too high.
- MMVF clusters having a remarkably improved strength can be obtained when the inorganic fibres are mixed with a liquid containing a binder which is a preferred embodiment according to the invention.
- the MMVF clusters thus obtained are very “strong” after drying and are hardly opened when mixed into the friction material formulation. It is believed that the improved strength of the MMVF clusters is caused by the binder on the fibre surface sticking together the fibres after drying.
- binder it is possible to use organic and inorganic binders which are known to the person skilled in the art.
- a single binder or a mixture of two or more binders may be used.
- suitable binders are acrylic resins such as acrylates or methacrylates, alkyd resins, saturated and unsaturated polyester resins, polyurethanes based on di- or polyisocyanates and di- or polyols, epoxy resins, silicone resins, urea resins, melamine resins, phenolic resins, waterglass, alkyl silicate binders, cellulose esters, such as esters of cellulose with acetic acid or butyric acid, polyvinyl resins such as polyolefins, polyvinylchloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetate, polyvinyl ether, polyvinyl ester, polyvinyl pyrrolidone and polystyrene resins and derivatives and cop
- binder examples include poly vinylacetate resin, vinylchloride-vinylacetate copolymer, polyacrylonitrile resin, polycarbonate resin, polyamide resin, butyral resin, polyurethane (PU) resins, vinylidenechloride-vinylchloride copolymer, styrene-butadiene copolymer, vinylidenechloride-acrylonitrile copolymer, vinylchloride-vinylacetate-maleic anhydride copolymer, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, benzoguanamine resin, epoxyacrylate resin, urethaneacrylate resin, poly-N-vinylcarbazole resin, polyvinylbutyral resin, polyvinylformal resin, polysulfone resin, casein, gelatin, ethylcellulose, carboxymethyl cellulose, vinylidenechloride-based polymer latex, acrylonitrile-but
- Suitable binders are e g SBR and PU based binders.
- the liquid containing a binder may be an aqueous or non-aqueous solution or dispersion and is preferably a latex, latex emulsion or polymer dispersion.
- the liquid is preferably water or an aqueous liquid.
- the liquid containing a binder is preferably a water based emulsion.
- the content of binder in the liquid may vary. Generally, the binder content in the liquid is suitably in the range of 10 to 90% by weight, preferably 30 to 60% by weight.
- the ratio of liquid to MMVF to be mixed may vary, but an appropriate ratio by weight of liquid to MMVF may be in the range of 1 to 30%, a range of 5 to 15% being preferred, wherein the liquid refers to the liquid employed, i.e. optionally including the binder and/or other additives.
- the liquid may also contain other additives, but generally it is not advantageous to add such further additives.
- the MMVF clusters according to the invention generally do not include MMVF having wetting agents or surfactants on the fibre surface. This is because wetting agents and surfactants generally weaken the strength of the MMVF clusters resulting in an opening of the clusters and a homogeneous distribution of the fibres in the friction material formulation. Accordingly, it is generally preferred that the liquid used for preparing MMVF clusters does not include wetting agents or surfactants.
- MMVF mixtures which include more than 80% by weight and up to 100% by weight, preferably more than 90% by weight of MMVF clusters and up to 100% by weight, based on the total weight of the MMVF mixture. That is, the MMVF mixture obtained includes 20% by weight or less and preferably 10% by weight or less of loose MMVF. In addition, it is preferable that the MMVF mixture obtained is essentially free of shots which means that shots of >125 ⁇ m are included in the inorganic fibre mixture in an amount of from 0 to at most 0 2% by weight.
- the described process of the invention even allows the preparation of MMVF mixtures containing approximately 100% by weight of MMVF clusters. With the process described, MMVF clusters having a small average size ( ⁇ 2 mm) can be prepared.
- the MMVF mixture containing MMVF clusters as described above may be used as is for the incorporation into the friction material formulation as discussed below. Since loose MMVF may also have a beneficial effect on friction materials with respect to reinforcement, it is also possible to mix the MMVF mixture mainly comprising MVMF clusters as described above with a common MMVF mixture mainly comprising loose MMVF in order to obtain a MMVF mixture with an adjusted content of MMVF clusters in accordance with the user's need. Thus, MMVF mixtures can be prepared and used for incorporation into the friction material formulation. Alternatively, it is of course also possible to incorporate MMVF mixtures containing MMVF clusters according to the process of the invention and normal loose MMVF mixtures into the friction material formulation separately.
- MMVF suitable for use in making MMVF clusters and/or for incorporating into the friction material as loose fibres may be made by any suitable method, for example by feeding a glass melt, rock melt or slag melt to a cascade spinner or a spinning cup and collecting the fibres thus formed. Shots may be removed by conventional sieving techniques.
- the friction material formulation refers to a mixture of the components used for preparing the friction material.
- the inorganic fibres preferably mineral fibres, or MMVF clusters, respectively
- the inorganic fibres or MMVF clusters are added to or mixed with the components.
- the order of mixing the components of the friction material formulation and the inorganic fibres or MMVF clusters, respectively, is not restricted. That is, the MMVF clusters may be e.g., added to the binding agent of the friction material and mixed, and at the same time or subsequently other components of the friction material formulation such as reinforcing fibres, fillers or frictional additives may be added. Any other order is also possible. It may however be advantageous to add the MMVF clusters to a pre-mix of all or most of the other components of the friction material composition in order to minimize the mechanical load applied to the inorganic fibre balls.
- the starting materials for the friction material other than the MMVF clusters are combined prior to adding the MMVF clusters, so as to preserve as much as possible the three-dimensional shape of the MMVF clusters.
- the MMVF clusters may be incorporated into the mixture at the same step as the other starting materials for the friction material.
- the MMVF clusters may be provided with a coating such as a binding agent to help to preserve the 3-dimensional shape of the MMVF clusters.
- 5% by weight to 100% by weight, preferably from 10% by weight to 100% by weight, of the total amount of mineral fibres added in the friction material formulation are MVMF clusters, the remainder being loose mineral fibres.
- the friction material may contain other inorganic fibres.
- 5% by weight to 100% by weight, preferably from 10% by weight to 100% by weight, of the total amount of inorganic fibres added in the friction material formulation are MMVF clusters, the remainder being loose inorganic fibres.
- the amount of MMVF clusters incorporated into the mixture prior to pressing and curing is preferably from 1 to 10 v/v % of the starting materials.
- the friction material refers to the product obtained after forming and hardening the friction material formulation in which the MMVF clusters have been incorporated and includes also those products wherein the friction materials was subjected to an after-treatment such as scorching, cutting, polishing, gluing on substrates.
- the hardening may be a simple hardening or solidification, e.g. by solvent removal from the formulation or cooling.
- the friction material formulation is hardened by curing the friction material formulation or the binding agent, respectively.
- the friction material may comprise one or more binding agents. After hardening, preferably during curing, the binding agents maintain the structural integrity under mechanical and thermal stress. The binding agent forms the matrix in which the other components are embedded.
- the binding agent may be organic or inorganic but usually and preferably an organic binding agent is used.
- Thermosetting and thermoplastic binding agents may be employed, thermosetting binding agents being preferred.
- suitable binding agents for the friction material formulation are phenolic resins including phenol-formaldehyde resins, e.g.
- novolac resins so-called COPNA resins (condense polynuclear aromatic resins), silicone-modified resins also referred to as phenolic siloxane resins which are reaction products of silicone oil or silicone rubber and phenolic resins, cyanate ester resins, epoxy-modified resins, such as epoxy-modified phenolic resins, epoxy resins in combination with specific curing agents such as anhydrides, polyimide resins, e.g. a product of a fluoro resin and calcium carbonate.
- Preferred binding agents are phenolic based resins, in particular phenol-formaldehyde tougheners such as epoxy resin or filled with wood flour.
- COPNA resins are often used in combination with graphite.
- the friction material formulation may comprise one or more types of reinforcing fibres.
- reinforcing fibres typically a mixture of different types of reinforcing fibres with complementing properties are used.
- Examples for reinforcing fibres are glass fibres, mineral fibres, metallic fibres, carbon fibres, aramid fibres, potassium titanate fibres, sepiolite fibres and ceramic fibres.
- Metallic components for reinforcement may also have a shape other than a fibre shape. As is usual in the art, in the present application all metallic components included in the friction materials are considered as metallic reinforcing fibres whatever their shape is, such as fibre, chip, wool, etc. Examples of metallic fibres include steel, brass and copper, preferably steel.
- Metallic fibres may be oxidised or phosphatised.
- An example of aramid fibres are Kevlar fibres.
- Ceramic fibres are typically made of metal oxides such as alumina or carbides such as silicon carbide.
- Reinforcing fibres are typically loose fibres, rather than fibre clusters.
- the friction material formulation of the invention may comprise loose mineral fibres as reinforcing fibres, in addition to the MMVF clusters for the reduction of wear.
- the friction material formulation may include reinforcing fibres that comprise loose MMVF as part of a mixture of different types of fibres.
- the friction material formulation may also include additives such as lubricants, abrasives, curing agents, crosslinkers, and solvents.
- Typical lubricants are graphite and metal sulphides such as antimony sulphide, tin sulphide, copper sulphide and lead sulphide.
- Abrasives typically have Mohs hardness values around 7-8.
- Typical abrasives are metal oxide abrasives and silicates abrasives, e.g. quartz, zirconium silicate, zirconium oxide, aluminium oxide and chromium oxide.
- typical fillers may be organic or inorganic and include barium sulphate, calcium carbonate, mica, vermiculite, alkali metal titanates, molybdenum trioxide, cashew dust, rubber dust, sillimanite, mullite, magnesium oxide, silica, and iron oxide.
- the fillers may play a role in modifying certain characteristics of the friction material, e.g. enhancement of heat stability or noise reduction. Therefore the specific filler or fillers to be used depends on the other constituents of the friction material.
- Mica, vermiculite, cashew dust, and rubber dust are known as noise suppressors.
- the friction material may have any suitable formulation.
- Preferred formulations include those referred to in the art as NAO/low-steel and NAO/non-steel.
- NAO refers to “non-asbestos organic”.
- NAO/low-steel and NAO/non-steel are particularly suitable for automotive applications such as brake pads and clutch linings.
- NAO/low-steel formulations typically include about 5 to 25 vol % of metallic components.
- NAO/non-steel formulations do not contain any steel.
- a suitable formulation with which to make the friction material is:
- the amount of MMVF clusters is preferably at least 1 wt %, such as at least 3 wt %, more preferably at least 5 wt %.
- the finished friction product preferably comprises less than 15 wt % MMVF clusters, such as less than 12 wt % MMVF clusters.
- Suitable wear-reduction applications for friction materials according to the invention include automotive brake pads, clutch linings, industrial friction materials, railway blocks, railway pads, and friction papers.
- the friction material of the invention is part of an automotive brake pad, more preferably in a NAO/non-steel or NAO/low-steel brake pad formulation for a passenger vehicle.
- the friction material of the invention preferably has a density of from 2.0 to 3.0 g/cm 3 .
- the friction material of the invention preferably has a porosity of from 10% to 25%, preferably from 15% to 25%.
- the friction material of the invention preferably has a hardness (HRS) of from 50 to 100.
- the friction material of the invention is particularly useful for reducing wear at elevated temperatures.
- the friction material is used to reduce wear at temperatures of at least 300° C., such as at least 500° C. Such temperatures may be found during periods of vehicle braking, in which the friction material of the invention is used as a brake pad for a passenger car.
- the quoted size distribution for the commercially available product is 8-16 mesh (1180-2360 ⁇ m), but measured values reveal a greater variation in size distribution (Table 2.1).
- the fibre clusters made according to the invention were all within the range 0.6 to 1 mm, with clusters outside of this range removed by sieving.
- Friction material pads were prepared as follows. All components, except for the fibre spheres or fibre clusters, were combined in a high-speed MTI mixer in two mixing steps. The commercially available fibre spheres (Examples 1B and 1C) or the fibre clusters according to the invention (Example 1A) were combined with the remaining components in a third mixing steps. The resulting mixture was filled into moulds and hot pressed. Following the hot press, curing was carried out (2 hours, 200° C.).
- the friction material pads were prepared as car brake pads for wear testing.
- Example Example 1B - Example 1C - 1A - fibre commercially commercially clusters according available fibre available fibre to the invention spheres spheres Density (g/cm 3 ) 2.17 2.19 2.21 Porosity (%) 23.2 22.7 22.0 Hardness (HRS) 63 stdev 5 55 stdev 6 69 stdev 12
- the brake pad that incorporated fibre clusters according to the invention exhibited lower wear in the SAE J2521 test setup compared to brake pads incorporating the same amount of commercially available fibre spheres having a broad distribution of sizes of fibre spheres.
- Example 2 compares the wear properties of friction materials comprising fibres only in loose form, as is known in the art, with the wear properties of friction materials comprising fibre clusters according to the present invention.
- Example 2 friction materials were made up according to a NAO non-steel formulation (Table 5) and either loose fibres or fibre clusters according to the invention.
- the resulting mixture was filled into moulds and pressed. Following pressing, a curing step was carried out (2 hours, 200°).
- Example 3 compares the wear properties of friction materials comprising fibres only in loose form, as is known in the art, with the wear properties of friction materials comprising fibre clusters according to the present invention.
- Example 3 friction materials were made up according to a NAO low-steel formulation (Table 9) and either loose fibres or fibre clusters according to the invention.
- Example 3A represents a friction material comprising loose MMVF, wherein the MMVF have fibre length 125 ⁇ 25 ⁇ m.
- Example 3B represents a friction material comprising MMVF clusters all of size from 0.6 mm to 1.0 mm.
- the MMVF forming the clusters have fibre length 300 ⁇ 50 ⁇ m.
- Example 3C represents a friction material comprising MMVF clusters all of size from 1.0 mm to 1.6 mm.
- the MMVF forming the clusters have fibre length 300 ⁇ 50 ⁇ m.
- the size range of the MMVF clusters was controlled by sieving.
- pad wear was lower for the examples 3B and 3C according to the invention, compared to the comparative example 3A that used only loose fibres and no fibre clusters.
Abstract
Description
- The invention relates to a friction material exhibiting reduced wear in use and to processes for preparation of such a friction material. The invention also relates to man-made vitreous fibre (MMVF) clusters suitable for use in preparation of these friction materials and for reduction of wear of the friction materials.
- Friction materials are widely used in a variety of applications such as in brake or clutch devices. They are often used for instance in the form of brake pads, brake shoes, brake linings, friction plates and clutch facings. They may be used in a variety of applications including industrial machines and transport machines or vehicles such as elevators, passenger vehicles and the like.
- One important characteristic of a friction material is that it should exhibit low wear in use. Wearing of the friction material can lead to an increase in emissions, which is undesirable. The present invention aims to produce friction materials which exhibit reduced wear.
- WO2011/042533 describes the use of inorganic fibre balls in a friction material for the purpose of reducing NVH (noise and vibration harshness). This document teaches to use normal lubricants and abrasives as fillers to adjust the wear properties of the friction material. There is also no requirement for the inorganic fibre balls to have any particular size distribution.
- WO2017/212029 and technical paper “White stone fibres for reduced wear in friction applications”, Persoon et al., EB2016-MDS-003, presented and published at the EuroBrake 2016, Milan, Italy, both describe one solution for reducing wear in friction materials. This involves using a different from normal fibre chemistry for man-made vitreous fibres (MMVF) that are incorporated into the friction material as reinforcing fibres. The fibres are incorporated as “loose” fibres and are of lower abrasiveness than other MMVF commonly used in friction materials such as brake pads, thereby reducing the wear.
- It is well known to use MMVF as components of formulations for friction materials. The present invention is based on the finding that inclusion of MMVF in the form of discrete clusters in the friction material formulation can lead to reduced wear, in comparison with including MMVF in the form of loose fibres.
- According to a first aspect of the invention we provide the use of MMVF clusters in a friction material formulation for the reduction of wear of said friction material in use.
- Thus, a friction material containing MMVF in the form of clusters will exhibit reduced wear in use in comparison with a friction material having the same formulation but containing the same percentage of the same MMVF in loose form. Wear can be determined according to standard tests such as the wear elements of SAE J2521: 2003-06, SAE J 2522: 2006-01, and SAE J 2707: 2005-02.
- Fibres of the MMVF type when incorporated into friction materials are conventionally included as loose fibres, namely single individual fibres which are not substantially entangled with each other. When included in a matrix, such loose fibres are sometimes referred to as dispersed fibres, because they are dispersed throughout the matrix. In contrast, the fibre clusters used according to the present invention are balls of agglomerated MMVF, which may be to some extent interwoven or entangled. They may therefore have the form of granules. Preferably they are regular in shape, for instance ovoid or spheroid (substantially spherical). When incorporated into a friction material, they may have a discoid shape.
- We have found that the size distribution of the MMVF clusters is important in optimising wear reduction. To be defined as a cluster, a collection of fibres should have a minimum dimension of at least 0.4 mm. We find that the best wear reduction performance is given by MMVF clusters of sizes in the range 0.6 to 1.6 mm, preferably 0.6 to 1.0 mm. Accordingly, preferably the MMVF clusters used in the invention are of size distribution in which at least 95 wt % of the MMVF clusters have size in the range 0.6 to 1.6 mm. Preferably at least 97 wt %, more preferably at least 98 wt %, and even more preferably substantially 100 wt % of the MMVF clusters have size in this range. Size can be determined by sieving. Provision of the defined size distribution can also be done by use of sieving.
- Thus according to a second aspect of the invention we provide a method for the preparation of a friction material comprising the step of incorporating MMVF clusters into a friction material formulation, wherein the MMVF clusters have a size distribution such that at least 95 wt % have size in the range 0.6 to 1.6 mm.
- According to a third aspect of the invention there is provided the use of MMVF clusters in the preparation of a friction material formulation, wherein the MMVF clusters have a size distribution such that at least 95 wt % have size in the range 0.6 to 1.6 mm.
- According to a fourth aspect of the invention there is provided a mixture of man-made vitreous fibres comprising from 1 to 100% by weight MMVF in the form of clusters, wherein at least 95 wt % of said clusters have size in the range 0.6 to 1.6 mm.
- The mixture may comprise at least 50 wt %, preferably at least 75 wt % and even 100 wt % MMVF in the form of clusters. The remainder is formed of MMVF in the form of loose fibres.
- According to a fifth aspect of the invention we provide a friction material obtainable by the method of the second aspect of the invention.
- In the method of the invention, at least 95 wt % of the MMVF clusters have a size in the range from 0.6 mm to 1.6 mm, preferably from 0.6 mm to 1.0 mm. Preferably all of the MMVF clusters used in the method have a size in that range. Size can be controlled using conventional sieving techniques. The size refers to the largest dimension of the man-made vitreous fibre clusters, which need not have a regular spherical shape.
- The inventors have found that, surprisingly, using MMVF clusters within this narrow size range brings benefits for wear reduction when the friction material is in use. In particular, the wear of the friction material itself is reduced. This is of current concern in the automotive industry, in which it is desirable to reduce the wear of brake pads to reduce particulate emissions to the environment. Using MMVF clusters within this narrow size range may contribute to wear rate reduction due to the size of the reservoir provided by the MMVF clusters, in which wear debris may accumulate rather than being lost to the environment.
- In the friction material made according to the invention preferably the level of MMVF clusters is less than 15 wt %, such as less than 12 wt %. It is possible to include loose fibres as well as MMVF clusters. In this case, it is preferred that the loose fibres are also MMVF, more preferably of the same type and composition as the MMVF that are used to form the clusters. In this case, it is also preferred that the total level of MMVF clusters and loose fibres is less than 15 wt %, preferably less than 12 wt %. Preferably the level of MMVF clusters in the friction material is at least 1 wt %, preferably at least 3 wt %, more preferably at least 5 wt %.
- Using a mixture of MMVF loose fibres and MMVF clusters is beneficial for achieving the wear reduction properties associated with the clusters alongside the strengthening properties associated with the loose fibres.
- When both MMVF clusters and loose MMVF are used, preferably at least 50 wt %, more preferably at least 75 wt %, of the blend is made up of MMVF clusters, with the balance being loose MMVF.
- The friction material may comprise other types of loose fibres, such as aramid fibres, steel fibres, carbon fibres, and other types of mineral fibres. For example, other fibre types may be used as reinforcing fibres. A mixture of different types of reinforcing fibres with complementing properties are used. Examples for reinforcing fibres other than MMVF are glass fibres, mineral fibres, metallic fibres, carbon fibres, aramid fibres, potassium titanate fibres, sepiolite fibres and ceramic fibres. Metallic components for reinforcement may also have a shape other than a fibre shape. As is usual in the art, in the present application all metallic components included in the friction material are considered as metallic reinforcing fibres whatever the shape thereof is (fibre, chips, wool, etc.). Examples of metallic fibres include steel, brass and copper. Since steel fibres often suffer from the drawback of rusting, zinc metal is often distributed over the friction material when steel fibres are used. Metallic fibres may be oxidized or phosphatized. An example of aramid fibres are Kevlar fibres. Ceramic fibres are typically made of metal oxides such as alumina or carbides such as silicon carbide.
- Preferably all of the loose fibres are loose MMVF.
- The MMVF used to form the clusters preferably have length in the range of 100 to 650 μm, preferably 100 to 350 μm.
- Fibre clusters made from medium length fibres (250-350 μm) can result in a particularly stable coefficient of friction. Using fibre clusters made from short or medium length fibres (100-350 μm) can result in wear reduction compared to using loose fibres.
- Fibre diameter is also typically in the range 3 to 10 microns.
- The fibre diameter and fibre length of the plurality of man-made vitreous fibres that make up each MMVF cluster are both number averages. The aspect ratio is calculated as the number average length divided by the number average diameter. The number average fibre length is preferably no greater than 200 μm. The number average fibre diameter is preferably no less than 4.5 μm. The aspect ratio is preferably no greater than 60, more preferably no greater than 40, more preferably no greater than 30.
- Generally the MMVF clusters are blended with the remainder of the friction material formulation in such a way as to remain as discrete and coherent clusters of MMVF in the final friction material. As is conventional, the friction material formulation is generally formed into the desired final form by moulding and compression. Preferably the MMVF clusters, and optionally any loose MMVF, are incorporated into the mixture of components at the final mixing step prior to pressing and curing, to preserve the shape of the MMVF clusters. Alternatively, the MMVF clusters may be coated with a suitable bonding agent prior to mixing, such that the clusters' shape is preserved even when combining into the mixture at the same time as the other components of the friction material.
- We find that in a product made according to the process of the invention the clusters remain as discrete and coherent clusters but rather than being of ovoid or substantially spherical form are in discoid form. Namely their diameter is often at least 3 times, sometimes at least 4 times the height. Height is defined as the direction within the friction material along which compression has been exerted.
- MMVF used for the fibre clusters in this invention may have a composition including for instance 35-45 wt % SiO2, 16-23 wt % Al2O3, 0.3-0.7 wt % TiO2, <1.5 wt % Fe2O3, 20 to 30 wt % CaO, in particular 25-27 wt % CaO, 1 to 5 wt % MgO, in particular 3-7 wt % MgO, <2.0 wt % Na2O, <0.6 wt % K2O, <0.3 wt % P2O5, <0.2 wt % MnO. Chemical properties can be ascertained using XRF.
- Suitable types of MMVF for the MMVF clusters include stone fibres, glass fibres, slag fibres and ceramic fibres. Preferably stone fibres are used.
- Preferably the composition of the fibres making up the man-made vitreous fibre clusters comprises less than 50 wt % SiO2 and greater than 15 wt % Al2O3. This may help to make the MMVF bio-soluble.
- Preferably the man-made vitreous fibre clusters comprise no more than 2 wt %, preferably no more than 1 wt %, of shot of size >63 μm.
- Fibres may be provided with known coatings.
- The fibre clusters for use in the method of the invention preferably have a moisture content of less than 0.05 wt %.
- In a preferred process for the preparation of MMVF clusters, MMVF (man-made vitreous fibres) are mixed in a mixer. By this mixing process loose MMVF are agitated or rolled against each other so that agglomeration occurs to form the MMVF clusters. The mixer preferably provides a circular motion.
- It is more preferred to mix the MMVF with a liquid in a mixer and drying the obtained mixture to obtain MMVF clusters. The presence of the liquid enhances the firmness of the clusters obtained. The liquid used should be vaporizable. A low viscosity liquid is preferable. Examples for suitable liquids are water and organic solvents, e g alcohols, water based emulsions and mixtures thereof.
- Preferred liquids are water and water based emulsions. The liquid and the MMVF may be simply fed into the mixer. It is also possible to spray the liquid on the MMVF which may cause a better preliminary distribution of the liquid on the fibres. It is further preferred that the liquid employed contains a binder since the binder further improves the firmness of the MMVF clusters obtained.
- The MMVF used for preparing the MMVF clusters are preferably relatively short fibres, such as a length of 100 to 500 μm, preferably 100 to 350 μm otherwise the liquid cannot be distributed well on the fibre surface. Appropriately, the MMVF are in the form of loose MMVF or predominately in the form of loose MMVF. In the preferred mixing step, the MMVF are mixed with the liquid, preferably containing a binder, so that the liquid is distributed on the surface of the fibres. In addition, the MMVF are moved, preferably by a circular motion, so that the MMVF agglomerate or ball up, respectively, to form the MMVF clusters. Hence, the mixing step preferably comprises mixing the MMVF with the liquid, preferably containing the binder, and rolling the MMVF on which the liquid is distributed to form the MMVF clusters. The liquid supports the formation of the clusters.
- In general, the mixing step may optionally comprise two stages: a first more vigorous mixing to achieve mixing of the liquid with the MMVF, and a second, more gentle, mixing or rolling in order to ball up the MMVF on which the liquid is distributed.
- The mixer employed in the mixing step may be any common mixing device generally known in the art, for instance a horizontal mixer or a vertical mixer. It may be useful that the mixer includes choppers, e.g. a vertical or horizontal mixer having choppers. Appropriately, the mixing time may be in the range of 1 to 20 minutes and preferably in the range of 2 to 8 minutes. Appropriately the head axle speed is in the range of 50-300 rpm. The mixing process preferably consists of a first stage with choppers rotation, e g., at 2500-3500 rpm or approximately at 3000 rpm, to distribute the liquid and a second stage without chopped activity for maximum ball formation. The mixing parameters however may vary depending on the type of MMVF, the mixer, the ball size desired, etc.
- If a liquid is used for the preparation, the product obtained containing MMVF clusters needs to be dried when discharged from the mixer because products with a too high liquid content cannot be tolerated in friction materials. In the drying step, the liquid is evaporated from the MMVF clusters for which commonly known methods can be used, e g drying in an oven (static drying), drying in a dispersion dryer or drying in a fluid bed dryer. The drying step may result in a complete removal of the liquid, though a small amount of liquid remaining in the MVMF clusters may be acceptable. When water is used as the liquid, the formed MMVF clusters are not very strong after drying so that the clusters may be opened too easily when they are mixed into a friction material formulation if the mechanical load is too high.
- MMVF clusters having a remarkably improved strength can be obtained when the inorganic fibres are mixed with a liquid containing a binder which is a preferred embodiment according to the invention. The MMVF clusters thus obtained are very “strong” after drying and are hardly opened when mixed into the friction material formulation. It is believed that the improved strength of the MMVF clusters is caused by the binder on the fibre surface sticking together the fibres after drying.
- As a binder, it is possible to use organic and inorganic binders which are known to the person skilled in the art. A single binder or a mixture of two or more binders may be used. Examples of suitable binders are acrylic resins such as acrylates or methacrylates, alkyd resins, saturated and unsaturated polyester resins, polyurethanes based on di- or polyisocyanates and di- or polyols, epoxy resins, silicone resins, urea resins, melamine resins, phenolic resins, waterglass, alkyl silicate binders, cellulose esters, such as esters of cellulose with acetic acid or butyric acid, polyvinyl resins such as polyolefins, polyvinylchloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetate, polyvinyl ether, polyvinyl ester, polyvinyl pyrrolidone and polystyrene resins and derivatives and copolymers of these polyvinyl resins, nitrocellulose, chlorinated rubbers, glucose and oil varnishes
- More specific examples of the binder include poly vinylacetate resin, vinylchloride-vinylacetate copolymer, polyacrylonitrile resin, polycarbonate resin, polyamide resin, butyral resin, polyurethane (PU) resins, vinylidenechloride-vinylchloride copolymer, styrene-butadiene copolymer, vinylidenechloride-acrylonitrile copolymer, vinylchloride-vinylacetate-maleic anhydride copolymer, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, benzoguanamine resin, epoxyacrylate resin, urethaneacrylate resin, poly-N-vinylcarbazole resin, polyvinylbutyral resin, polyvinylformal resin, polysulfone resin, casein, gelatin, ethylcellulose, carboxymethyl cellulose, vinylidenechloride-based polymer latex, acrylonitrile-butadiene copolymer, styrene butadiene rubber (SBR), vinyltoluene-styrene copolymer, soybean oil-modified alkyd resin, nitrated polystyrene resin, polymethylstyrene resin, polyisoprene resin, polyarylate resin, polyhaloarylate resin, polyaryl ether resin, polyvinylacrylate resin, and polyesteracrylate resin. Suitable binders are e g SBR and PU based binders. The liquid containing a binder may be an aqueous or non-aqueous solution or dispersion and is preferably a latex, latex emulsion or polymer dispersion. The liquid is preferably water or an aqueous liquid. The liquid containing a binder is preferably a water based emulsion.
- The content of binder in the liquid may vary. Generally, the binder content in the liquid is suitably in the range of 10 to 90% by weight, preferably 30 to 60% by weight. The ratio of liquid to MMVF to be mixed may vary, but an appropriate ratio by weight of liquid to MMVF may be in the range of 1 to 30%, a range of 5 to 15% being preferred, wherein the liquid refers to the liquid employed, i.e. optionally including the binder and/or other additives.
- Apart from the binder, the liquid may also contain other additives, but generally it is not advantageous to add such further additives. In particular, the MMVF clusters according to the invention generally do not include MMVF having wetting agents or surfactants on the fibre surface. This is because wetting agents and surfactants generally weaken the strength of the MMVF clusters resulting in an opening of the clusters and a homogeneous distribution of the fibres in the friction material formulation. Accordingly, it is generally preferred that the liquid used for preparing MMVF clusters does not include wetting agents or surfactants.
- With the process of preparing MMVF clusters described above, wherein preferably MMVF are mixed with the binder-containing liquid and subsequently dried, it is possible to prepare MMVF mixtures which include more than 80% by weight and up to 100% by weight, preferably more than 90% by weight of MMVF clusters and up to 100% by weight, based on the total weight of the MMVF mixture. That is, the MMVF mixture obtained includes 20% by weight or less and preferably 10% by weight or less of loose MMVF. In addition, it is preferable that the MMVF mixture obtained is essentially free of shots which means that shots of >125 μm are included in the inorganic fibre mixture in an amount of from 0 to at most 0 2% by weight. The described process of the invention even allows the preparation of MMVF mixtures containing approximately 100% by weight of MMVF clusters. With the process described, MMVF clusters having a small average size (<2 mm) can be prepared.
- The MMVF mixture containing MMVF clusters as described above may be used as is for the incorporation into the friction material formulation as discussed below. Since loose MMVF may also have a beneficial effect on friction materials with respect to reinforcement, it is also possible to mix the MMVF mixture mainly comprising MVMF clusters as described above with a common MMVF mixture mainly comprising loose MMVF in order to obtain a MMVF mixture with an adjusted content of MMVF clusters in accordance with the user's need. Thus, MMVF mixtures can be prepared and used for incorporation into the friction material formulation. Alternatively, it is of course also possible to incorporate MMVF mixtures containing MMVF clusters according to the process of the invention and normal loose MMVF mixtures into the friction material formulation separately.
- MMVF suitable for use in making MMVF clusters and/or for incorporating into the friction material as loose fibres may be made by any suitable method, for example by feeding a glass melt, rock melt or slag melt to a cascade spinner or a spinning cup and collecting the fibres thus formed. Shots may be removed by conventional sieving techniques.
- The friction material formulation refers to a mixture of the components used for preparing the friction material. By incorporating the inorganic fibres, preferably mineral fibres, or MMVF clusters, respectively, into the friction material, the inorganic fibres or MMVF clusters, respectively, are added to or mixed with the components. The order of mixing the components of the friction material formulation and the inorganic fibres or MMVF clusters, respectively, is not restricted. That is, the MMVF clusters may be e.g., added to the binding agent of the friction material and mixed, and at the same time or subsequently other components of the friction material formulation such as reinforcing fibres, fillers or frictional additives may be added. Any other order is also possible. It may however be advantageous to add the MMVF clusters to a pre-mix of all or most of the other components of the friction material composition in order to minimize the mechanical load applied to the inorganic fibre balls.
- Preferably, all of the starting materials for the friction material other than the MMVF clusters are combined prior to adding the MMVF clusters, so as to preserve as much as possible the three-dimensional shape of the MMVF clusters. Alternatively, the MMVF clusters may be incorporated into the mixture at the same step as the other starting materials for the friction material. In this case, the MMVF clusters may be provided with a coating such as a binding agent to help to preserve the 3-dimensional shape of the MMVF clusters.
- In a preferred embodiment, 5% by weight to 100% by weight, preferably from 10% by weight to 100% by weight, of the total amount of mineral fibres added in the friction material formulation are MVMF clusters, the remainder being loose mineral fibres. In addition, the friction material may contain other inorganic fibres. In another embodiment it may be suitable that 5% by weight to 100% by weight, preferably from 10% by weight to 100% by weight, of the total amount of inorganic fibres added in the friction material formulation are MMVF clusters, the remainder being loose inorganic fibres.
- In the method of the invention, the amount of MMVF clusters incorporated into the mixture prior to pressing and curing is preferably from 1 to 10 v/v % of the starting materials.
- The friction material refers to the product obtained after forming and hardening the friction material formulation in which the MMVF clusters have been incorporated and includes also those products wherein the friction materials was subjected to an after-treatment such as scorching, cutting, polishing, gluing on substrates. The hardening may be a simple hardening or solidification, e.g. by solvent removal from the formulation or cooling. Preferably the friction material formulation is hardened by curing the friction material formulation or the binding agent, respectively.
- The friction material may comprise one or more binding agents. After hardening, preferably during curing, the binding agents maintain the structural integrity under mechanical and thermal stress. The binding agent forms the matrix in which the other components are embedded.
- The binding agent may be organic or inorganic but usually and preferably an organic binding agent is used. Thermosetting and thermoplastic binding agents may be employed, thermosetting binding agents being preferred. Examples of suitable binding agents for the friction material formulation are phenolic resins including phenol-formaldehyde resins, e.g. novolac resins, so-called COPNA resins (condense polynuclear aromatic resins), silicone-modified resins also referred to as phenolic siloxane resins which are reaction products of silicone oil or silicone rubber and phenolic resins, cyanate ester resins, epoxy-modified resins, such as epoxy-modified phenolic resins, epoxy resins in combination with specific curing agents such as anhydrides, polyimide resins, e.g. a product of a fluoro resin and calcium carbonate. Preferred binding agents are phenolic based resins, in particular phenol-formaldehyde tougheners such as epoxy resin or filled with wood flour. COPNA resins are often used in combination with graphite.
- In addition, the friction material formulation may comprise one or more types of reinforcing fibres. Typically a mixture of different types of reinforcing fibres with complementing properties are used. Examples for reinforcing fibres are glass fibres, mineral fibres, metallic fibres, carbon fibres, aramid fibres, potassium titanate fibres, sepiolite fibres and ceramic fibres. Metallic components for reinforcement may also have a shape other than a fibre shape. As is usual in the art, in the present application all metallic components included in the friction materials are considered as metallic reinforcing fibres whatever their shape is, such as fibre, chip, wool, etc. Examples of metallic fibres include steel, brass and copper, preferably steel. Since steel fibres often suffer from the drawback of rusting, zinc metal is often distributed over the friction material when steel fibres are used. Metallic fibres may be oxidised or phosphatised. An example of aramid fibres are Kevlar fibres. Ceramic fibres are typically made of metal oxides such as alumina or carbides such as silicon carbide. Reinforcing fibres are typically loose fibres, rather than fibre clusters.
- The friction material formulation of the invention may comprise loose mineral fibres as reinforcing fibres, in addition to the MMVF clusters for the reduction of wear. The friction material formulation may include reinforcing fibres that comprise loose MMVF as part of a mixture of different types of fibres.
- The friction material formulation may also include additives such as lubricants, abrasives, curing agents, crosslinkers, and solvents. Typical lubricants are graphite and metal sulphides such as antimony sulphide, tin sulphide, copper sulphide and lead sulphide. Abrasives typically have Mohs hardness values around 7-8. Typical abrasives are metal oxide abrasives and silicates abrasives, e.g. quartz, zirconium silicate, zirconium oxide, aluminium oxide and chromium oxide.
- Other typical fillers may be organic or inorganic and include barium sulphate, calcium carbonate, mica, vermiculite, alkali metal titanates, molybdenum trioxide, cashew dust, rubber dust, sillimanite, mullite, magnesium oxide, silica, and iron oxide. The fillers may play a role in modifying certain characteristics of the friction material, e.g. enhancement of heat stability or noise reduction. Therefore the specific filler or fillers to be used depends on the other constituents of the friction material. Mica, vermiculite, cashew dust, and rubber dust are known as noise suppressors.
- The friction material may have any suitable formulation. Preferred formulations include those referred to in the art as NAO/low-steel and NAO/non-steel. “NAO” refers to “non-asbestos organic”. NAO/low-steel and NAO/non-steel are particularly suitable for automotive applications such as brake pads and clutch linings. NAO/low-steel formulations typically include about 5 to 25 vol % of metallic components. NAO/non-steel formulations do not contain any steel.
- A suitable formulation with which to make the friction material is:
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Amount min Component (% v/v) Amount max (% v/v) Novolac resin 10 20 Aramid fibre 1 6 Solid lubricants 6 18 Friction particles 1 20 Potassium titanate 8 20 Abrasives 3 15 Fillers 10 25 Promaxon ®-D (inorganic porous 1 6 particles) MMVF clusters and optional 8 18 loose MMVF Total - In the finished friction product, the amount of MMVF clusters is preferably at least 1 wt %, such as at least 3 wt %, more preferably at least 5 wt %. The finished friction product preferably comprises less than 15 wt % MMVF clusters, such as less than 12 wt % MMVF clusters.
- Suitable wear-reduction applications for friction materials according to the invention include automotive brake pads, clutch linings, industrial friction materials, railway blocks, railway pads, and friction papers. Preferably, the friction material of the invention is part of an automotive brake pad, more preferably in a NAO/non-steel or NAO/low-steel brake pad formulation for a passenger vehicle.
- The friction material of the invention preferably has a density of from 2.0 to 3.0 g/cm3.
- The friction material of the invention preferably has a porosity of from 10% to 25%, preferably from 15% to 25%.
- The friction material of the invention preferably has a hardness (HRS) of from 50 to 100.
- The friction material of the invention is particularly useful for reducing wear at elevated temperatures. Preferably the friction material is used to reduce wear at temperatures of at least 300° C., such as at least 500° C. Such temperatures may be found during periods of vehicle braking, in which the friction material of the invention is used as a brake pad for a passenger car.
- Example 1 compares friction materials comprising fibre clusters having diameters all within the range 0.6 to 1 mm, according to aspects 2-5 of the invention, labelled in the data as Example 1A, with comparative friction materials comprising commercially available fibre spheres (Jiangsu REK High-Tec Materials Co., Ltd.) having a broad range of diameters, labelled in the data as Examples 1B and 10. A different product type of commercially available fibre spheres was used in each of Examples 1B and 10.
- The quoted size distribution for the commercially available product is 8-16 mesh (1180-2360 μm), but measured values reveal a greater variation in size distribution (Table 2.1).
- The fibre clusters made according to the invention were all within the range 0.6 to 1 mm, with clusters outside of this range removed by sieving.
- Friction materials were prepared using a NAO/non-steel formulation (Table 1).
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TABLE 1 NAO/non-steel formulation for wear tests of example 1. Component Amount (% v/v) Novolac resin 16 Aramid fibre 3 Solid lubricants 12 Friction particles 10 Potassium titanate 17 Abrasives 11 Fillers 16 Promaxon ®-D (inorganic porous particles) 5 Commercially available fibre spheres, or 10 fibre clusters according to the invention Total 100 - Friction material pads were prepared as follows. All components, except for the fibre spheres or fibre clusters, were combined in a high-speed MTI mixer in two mixing steps. The commercially available fibre spheres (Examples 1B and 1C) or the fibre clusters according to the invention (Example 1A) were combined with the remaining components in a third mixing steps. The resulting mixture was filled into moulds and hot pressed. Following the hot press, curing was carried out (2 hours, 200° C.).
- The friction material pads were prepared as car brake pads for wear testing.
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TABLE 2.1 measured size distribution of commercially available fibre spheres Fibre ball distribution >600 mu >1000 mu >1600 mu <600 mu <1000 mu <1600 mu <2360 mu >2360 mu (%) (%) (%) (%) (%) Example 1B 3.2 1.5 14.0 71.5 9.0 Example 1C 7.5 17.0 26.5 39.5 9.5 -
TABLE 2.2 number average fibre diameter and length of fibre spheres and fibre clusters used in the friction materials for Example 1 Number average Number average Aspect fibre length, μm fibre diameter, μm ratio L/D 1A - fibre clusters 118 4.66 25 according to the invention 1B - commercially 305 4.21 72 available fibre spheres 1C - commercially 244 3.70 66 available fibre spheres -
TABLE 2.3 measured properties of friction materials prepared for Example 1 Example Example 1B - Example 1C - 1A - fibre commercially commercially clusters according available fibre available fibre to the invention spheres spheres Density (g/cm3) 2.17 2.19 2.21 Porosity (%) 23.2 22.7 22.0 Hardness (HRS) 63 stdev 5 55 stdev 6 69 stdev 12 -
TABLE 3 wear results from SAE J2521 testing Example 1B - Example 1C - Example 1A - fibre commercially commercially clusters according available fibre available fibre to the invention spheres spheres μ- (μm) 0.39 0.39 0.39 mean Pad (g) 2.5 2.8 3.4 wear Pad (mm) 0.25 0.28 0.33 wear Disc (g) 1.5 1.4 1.9 wear - As can be seen from Table 3, the brake pad that incorporated fibre clusters according to the invention exhibited lower wear in the SAE J2521 test setup compared to brake pads incorporating the same amount of commercially available fibre spheres having a broad distribution of sizes of fibre spheres.
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TABLE 4 wear results from AKM (SAE J2522) test Example 1A - Example 1B - Example 1C - fibre clusters commercially commercially according to available fibre available fibre the invention spheres spheres Disc wear (g) 3.0 3.0 2.9 Overall mu (mu) 0.41 0.42 0.44 (average) μ 80 kph, 30 Bar, (mu) 0.41 0.43 0.44 100° (Av) - Example 2 compares the wear properties of friction materials comprising fibres only in loose form, as is known in the art, with the wear properties of friction materials comprising fibre clusters according to the present invention.
- The samples are labelled as follows:
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- Example 2A—loose fibres (short); the fibres making up the clusters have length 125±25 μm;
- Example 2B—fibre clusters of size from 0.6 mm to 1.0 mm, made using the same fibres as 2A (short); the fibres making up the clusters have length 125±25 μm;
- Example 2C—fibre clusters of size from 0.6 mm to 1.0 mm, made with medium length fibres; the fibres making up the clusters have length 300±50 μm;
- Example 2D—fibre clusters of size from 0.6 mm to 1.0 mm, made with long fibres; the fibres making up the clusters have length 500±150 μm.
- In Example 2, friction materials were made up according to a NAO non-steel formulation (Table 5) and either loose fibres or fibre clusters according to the invention.
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TABLE 5 friction material composition for Example 2 wear tests Component Amount (% v/v) Novolac resin 16 Aramid fibre 3 Solid lubricants 12 Friction particles 10 Potassium titanate 17 Abrasives 11 Fillers 16 Promaxon ®-D (inorganic porous particles) 5 10 Total 100 - The friction materials were prepared as follows. All components, except for the loose fibres or fibre clusters, were mixed in two stages (total time 4 minutes, 2000 rpm). The loose fibres or fibre clusters were incorporated into the mixture in a third mixing step (total time 1 minute, 500 rpm).
- The resulting mixture was filled into moulds and pressed. Following pressing, a curing step was carried out (2 hours, 200°).
- Three tests giving wear results were conducted in sequence using the same friction material pads: first test SAE J2521 Dynamometer, second test SAE J2522 Dynamometer, third test Krauss wear 150/300/500° C.
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TABLE 6 wear results from SAE J2521 Dynamometer tests Example 2A Example 2B Example 2C Example 2D (loose (fibre (fibre (fibre fibres) clusters) clusters) clusters) μ-mean (μ) 0.42 0.40 0.39 0.38 Pad (g) 4.21 2.89 3.38 2.72 wear Pad (mm) 0.41 0.29 0.34 0.27 wear Disc (g) 3.4 2.0 2.1 1.2 wear -
TABLE 7 wear results from SAE J2522 (AKM) Dynamometer tests Example 2A Example 2B Example 2C Example 2D (loose (fibre (fibre (fibre fibres) clusters) clusters) clusters) Pad wear (g) 8.48 8.94 8.26 8.26 Disc wear (g) 3.3 3.4 2.4 2.5 Overall (μ) 0.45 0.43 0.42 0.43 mu (average) μ 80 kph, (μ) 0.45 0.43 0.42 0.43 30 Bar, 100° (Av) -
TABLE 8 wear results from Krauss wear tests Example Example Example Example 2A 2B 2C 2D (loose (fibre (fibre (fibre fibres) clusters) clusters) clusters) Wear 150° C. μ (μ) 0.496 0.472 0.450 0.455 Average Pad (mg) 12.1 13.1 12.9 13.5 wear/brake Disc (g) 4.6 5.2 4.4 5.1 wear Wear 300° C. μ (μ) 0.415 0.416 0.399 0.408 Average Pad (mg) 22.3 21.8 25.3 23.0 wear/brake Disc (g) 2.9 2.6 3.0 3.7 wear Wear 500° C. μ (μ) 0.442 0.443 0.444 0.434 Average Pad (mg) 67.1 61.0 57.9 68.1 wear/brake Disc (g) 2.2 1.6 1.4 2.0 wear Total wear Pad (%) 100 94 95 103 wear/brake Disc (%) 100 86 84 109 wear - These results show that using fibre clusters made from medium length fibres (Example 2C) resulted in the most stable coefficient of friction and using fibre clusters made from short or medium length fibres resulted in wear reduction compared to using loose fibres.
- Example 3 compares the wear properties of friction materials comprising fibres only in loose form, as is known in the art, with the wear properties of friction materials comprising fibre clusters according to the present invention.
- In Example 3, friction materials were made up according to a NAO low-steel formulation (Table 9) and either loose fibres or fibre clusters according to the invention.
- Example 3A represents a friction material comprising loose MMVF, wherein the MMVF have fibre length 125±25 μm.
- Example 3B represents a friction material comprising MMVF clusters all of size from 0.6 mm to 1.0 mm. The MMVF forming the clusters have fibre length 300±50 μm.
- Example 3C represents a friction material comprising MMVF clusters all of size from 1.0 mm to 1.6 mm. The MMVF forming the clusters have fibre length 300±50 μm.
- The size range of the MMVF clusters was controlled by sieving.
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TABLE 9 friction material composition for Example 3 wear tests Component Amount (% v/v) Total 100 Cellulose 7.0 Barites 8.0 Steel Fibre 3.0 Friction particle 6.0 Resin 18.0 Petrol Coke 22.0 CPX 24 5.0 Sponge Iron powder 4.0 Brass chips 3.0 Mica 8.0 Alumina Oxide 1.0 Black Iron Oxide 5.0 Loose fibres, or fibre clusters according to 10.0 the invention - The friction materials were prepared by mixing all of the ingredients, except for the loose fibres or fibre clusters, in two mixing steps in a mixer (total time 2 minutes, 2000 rpm). The loose fibres or fibre clusters were added in a third mixing step (1 minute, 1000 rpm). The resulting mixture was filled into moulds and pressed. Curing (2 hours, 200° C.) followed the pressing stage.
- The same friction material pads were used in sequence for three tests: first test SAE J2521, second test SAE J2522, third test Krauss wear 150/300/500° C.
- The wear measurements from each of the three tests are summarised in Table 10.
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TABLE 10 wear results from SAE J2521 Dynamometer tests, SAE J2522 (AKM) Dynamometer tests, and Krauss wear tests Example 3B Example 3C Example 3A (invention) (invention (comparative) Fibre clusters Fibre clusters Loose fibres 0.6-1.0 mm 1.0-1.6 mm Pad wear SAE 7.9 7.9 8.3 J2521 (NVH) (g) Pad wear SAE 16.1 14.1 12.3 J2522 (AKM) (g) Pad wear Krauss 72.8 64.7 66.7 tests (g) Total Pad wear (g) 96.8 86.7 87.3 Total Pad wear 100 90 90 (%) Disc wear SAE 12.7 12.4 12.7 J2521 (NVH) (g) Disc wear SAE 2.9 2.7 3.0 J2522 (AKM) (g) Disc wear Krauss 6.9 9.1 9.4 tests (g) Total Disc wear 22.5 24.2 25.1 (g) Total Disc wear 100 108 112 (%) - As can be seen, pad wear was lower for the examples 3B and 3C according to the invention, compared to the comparative example 3A that used only loose fibres and no fibre clusters.
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